Rail bed maintenance and construction requires moving various materials such as gravel, ties and the like to work locations along the rail bed, and moving other materials such as used ties, off the rail bed. The materials are typically transported in open top rail cars called gondola cars. Where small quantities of material are involved a single gondola car, or a truck adapted for rail travel, with an attached handling arm can be utilized satisfactorily. Where larger quantities are required, it is desirable to move a string of cars, and preferably also provide a machine with a handling arm capable of unloading or loading the material as may be required.
U.S. Pat. No. 6,190,106 to Richardson et al., and U.S. Pat. No. 6,561,742 to Crawford et al. disclose loading machines with handling arms rotatable about the apparatus to load and unload as required from the front, rear or sides of the apparatus. The loading machines move along the top edges of the sidewalls of a gondola car as required. Ramps are provided to allow the loading machines to climb into position atop the sidewalls, however the machines of Richardson et al. and Crawford et al. are not able to cross from one gondola car in a string to the next.
To provide satisfactory service the loading machine should be able to travel from one car to the next to load or unload the material from a string of cars. U.S. Pat. No. 4,099,635 to Leonard et al. discloses a loading machine apparatus that has the ability to move along the top edges of the sidewalls of a gondola car, and across the gap between the gondola cars in a string such that same can be conveniently used to unload or load a string of gondola cars, however no means is disclosed for positioning the apparatus on the top of the sidewalls.
Backhoes have also been adapted to travel along the top edges of gondola car sidewalls. Such an adapted backhoe is disclosed in U.S. Pat. No. 4,190,394 to Herzog et al. The backhoe is moved into position on the top edges of the gondola car sidewalls by manipulating the boom and bucket of the backhoe. Similar manipulation moves the backhoe across the gaps between cars. To move onto the gondola car, the entire machine is raised a considerable distance off the ground to a height equal to the height of the gondola car, and balanced on the front bucket and rear boom of the backhoe. Stability of the backhoe while raising same to the top of the gondola car is thus a concern. Slot trains are also known comprising cars that have no end walls, and have a substantially continuous floor from one end of the string to the other. An excavator or like machine with a handling arm is simply driven along the floor, loading or unloading as required. Material brought in must be trans-loaded onto the slot train from a transport train that carries the material to the work site. Similarly, material picked up from the rail bed and loaded in the slot train must be trans-loaded onto a transport train to be hauled away. Considerable extra time is thus required.
Loading machines are also known that include a lengthy frame that can be extended forward and rearward with respect to the loading machine. The loading machine and frame are mounted on wheels that travel along the top of gondola car sidewalls similar to the apparatus of Leonard et al. To move from one car to the next, the frame is extended ahead of the loading machine across the gap separating the cars such that it is supported by the gondola cars on each side of the gap. Once the frame is in place on both cars, the loading machine is moved along the frame across the gap and onto the next gondola car where it can operate to load or unload that car. To maneuver the apparatus onto a second string of cars, the first string must be backed up to the second string and the apparatus moved onto the second string, the first string must be moved away, dropped, and the engine re-attached to the second string. Considerable time is thus required to move the apparatus to a fresh string of cars.